This project is to investigate the physico-chemical basis of cell fusion phenomena in model membrane as well as biological membrane systems. The project consists of a) Studies of membrane fusion between two spherical phospholipid membranes induced both thermally and chemically, b) a study of fusion between phospholipid bilayer and vesicle membranes, c) expansion and fusion of platelets and erythrocyte ghosts with a similar approach taken in the model membrane fusion studies. Mechanisms of fusion will be studied in terms of membrane instability, fluidity and hydrophobic interaction. Model membranes will be comprised of natural and synthetic phospholipids and membrane proteins. The platelets and erythrocytes will be extracted from animal blood. The properties to be measured and the methods to be used are electrical properties (capacitance and conductance of spherical membranes and planar bilayers during the contact and fusion), and microscopic observation and electron microscopy for the fusion, the spectroscopic observation for membrane aggregation, and monolayer properties (expansion, surface tension and viscosity) to correlate membrane fusion mechanism to the membrane hydrophobicity and fluidity.